Magnetic recording and reproducing requires that the magnetic head contact the recording medium, e.g. a floppy disk, very accurately in order to maximize track density. Variations introduced by dimensional and positional errors result in mistracking and increased access time. A conventional magnetic head supporting device for a floppy disk player will be described with reference to FIGS. 1 and 2.
A carriage 1, namely a supporting member, is made of a synthetic resin substantially in the form of a rectangular plate. A front bearing arm 2 and a rear bearing arm 3 are formed integrally with the carriage 1 so as to project from one side surface of the carriage 1. Oil retaining bearings 4 and 5 are force fitted in the front and rear bearing arms 2 and 3, respectively. A guide shaft 7, horizontally mounted on a chassis 6 (see FIG. 2), is received through the oil retaining bearings 4 and 5 to guide the carriage 1 for horizontal movements in directions indicated by a double-headed arrow a. A lower magnetic head 8 is attached, adhesively or likewise, to the upper surface of the front end of the carriage 1.
A hinge 10, made of a flat spring, is fixed to the upper surface of the rear end wall of the carriage 1 with screws. An arm 11 is fixed at its rear end to the hinge 10. Thus, the arm 11 is supported on the carriage 1 by the hinge 10 so as to be swingable in a vertical plane as indicated by arrows b and c in FIG. 2. The arm 11 is made of a synthetic resin in the form of a rectangular plate. Projection 12 is integral with the arm 11 and projects from one side surface thereof. At the rear end of the carriage 1 is a torsion coil spring 13 which applies pressure through one end 13a to the arm 11, biasing arm 11 downward (i.e. direction C) on the hinge 10.
A magnetic head 15 is held elastically on a magnetic head holding member 14 made of a flat spring and attached to the lower surface of the front end of the arm 11. The magnetic head holding member 14 is designated generally as a gimbal and is typically formed by punching a rectangular shape into a flat, phosphor-bronze spring or stainless spring. As illustrated in FIG. 1, the magnetic head holding member 14 consists integrally of a magnetic head holding part 16, a fixing part 17 formed in the shape of a rectangular frame surrounding the holding part 16, and an elastic functional part 18, which interconnects the holding part 16 and the fixing part 17. Holding part 16 and the elastic functional part 18 are connected by a pair of connecting parts 19 on a line X'. The elastic functional part 18 and the fixing part 17 are connected by a pair of connecting parts 20 on a line Y' extending at right angles to the line X'. The magnetic head 15 is attached adhesively or likewise to the underside (as viewed in the figures) of the holding part 16 with the head's center on the center 0 of the holding part 16. The fixing part 17 is fixed adhesively or likewise to the lower surface of the front end of the arm 11.
Referring now to FIG. 2, a floppy disk 22 is contained within a cartridge 23. The floppy disk 22 is a recording medium made of a magnetic sheet. The cartridge 23 is mounted horizontally on the chassis 6 with the floppy disk 22 placed horizontally on a turntable 24. Then, upper and lower magnetic heads 15 and 8 engage the cartridge 23, entering the cartridge through upper and lower openings 25 and 26 to contact with the respective upper and lower sides of the disk 22. The cartridge 23 is adapted to be inserted into a cartridge holder, not shown in this figure. The projection 12 (FIG. 1) rests on part of the upper surface of the cartridge holder. Accordingly, when the cartridge 23 is lowered in a direction indicated by arrow d, from an upper position indicated by alternate long and short dashed lines to a working position indicated by continuous lines, arm 11 is turned by the torsion coil spring 13, in the direction indicated by arrow c, from an upper position indicated by alternate long and short dashed lines to a lower position indicated by continuous lines.
After the cartridge 23 has thus been loaded on the chassis 6, a motor for driving the turntable 24 is actuated to rotate the floppy disk 22 within the cartridge 23. The carriage 1 is moved horizontally by a carriage driving mechanism, not shown, in a direction indicated by the arrow a to move the upper and lower heads 15 and 8 radially with respect to the disk 22, enabling the desired recording or reproducing operation. Since the magnetic head 15 is held on the magnetic head holding member 14 so as to be tiltable in directions indicated by double-headed arrows X and Y and so as to be moveable in directions indicated by a double-headed arrow Z (FIG. 1), the magnetic head 15 is held very satisfactorily in elastic contact with the flexible floppy disk 22.
As noted above, high quality recording and reproducing require that dimensional and positional errors in the contact between the magnetic head and the recording medium be minimized. However, the conventional supporting device described above is inherently inaccurate, permitting dimensional variations in assembly and in ambient temperature and humidity conditions to adversely affect the contact and positioning of the magnetic head and the recording medium. The difficulty of the conventional device is more fully described with reference to FIGS. 1 and 2.
The hinge 10 is screwed to the upper surface of the rear end wall of the carriage 1. The arm 11 is screwed at its rear end to the hinge 10. The magnetic head holding member 14 is attached adhesively or likewise to the lower surface of the front end of the arm 11. All of these fastening steps result in troublesome assembly work. Furthermore, as is well known, since the magnetic head 15 needs to be positioned with respect to the floppy disk 22 highly accurately, the hinge 10, the arm 11 and the magnetic head holding member 14 need to be assembled highly accurately, a troublesome and difficult requirement. Also, since it is inevitable that there will be both dimensional and positional errors between these parts in their assembly, a troublesome adjustment is required.
Conventionally, the arm 11 is formed by molding a synthetic resin. As a result, the arm 11 is liable to expand or to contract due to variations in temperature and/or the humidity. This expansion and contraction is likely to cause variations in dimensions which require high accuracy such as, for example, the distance L.sub.1, between the center of the magnetic head holding member 14 and the center line of the bolt holes for receiving the screws for fastening the arm 11 to the hinge 10, and the distance W.sub.1 between the respective centers of the bolt holes (FIG. 1). These variations cause problems in the tracking of the floppy disk 22 magnetic tracks by the head 15. These tracking variations reduce the interchangeability characteristics of the floppy disk 22.
Thus, in the conventional magnetic head supporting device of the type having upper and lower magnetic heads, as described above, the condition of contact of the upper and lower magnetic heads 15 and 8 with the floppy disk 22 is deteriorated by the relative positional variation (offset) between the upper and lower magnetic heads 15 and 8 due to the expansion or contraction of the arm 11.
Another aspect of the conventional magnetic head supporting device which contributes to undesirable variations in position involves the motion of the carriage 1 along guide shaft 7, best seen with reference to FIG. 1. In this conventional design, carriage front bearing arm 2 and rear bearing arm 3 are force-fitted with oil retaining bearings 4 and 5, respectively. The guide shaft 7, horizontally mounted on the chassis 6 (FIG. 2), is received through the oil retaining bearings 4 and 5 to guide the carriage 1 for horizontal movement in directions indicated by a double-headed arrow a. As shown in FIG. 1, the conventional shaft-bearing relationship permits undesirable movement in the directions indicated by arrows e and f. These positional variations, which result from bearing-insertion error and subsequent bearing wear, produce tracking errors which reduce signal reproduction quality and which restrict floppy disk 22 interchangeability.